What is the step-by-step procedure for cannulated screw (CC) fixation in a patient with an intracapsular neck of femur fracture?

Cannulated Screw Fixation for Intracapsular Femoral Neck Fracture: Step-by-Step Procedure

Cannulated screw fixation is the treatment of choice for undisplaced or minimally displaced intracapsular femoral neck fractures (Garden I-II), using three fully-threaded 6.5-7.0mm screws in a modified triangular configuration with the apex positioned superiorly to avoid creating a stress riser in the subtrochanteric region. 1, 2

Pre-Operative Preparation

Patient Selection and Timing

• Confirm the fracture is undisplaced or minimally displaced (Garden I-II) - displaced fractures require arthroplasty, not screw fixation 1
• Perform surgery within 24-48 hours of admission for optimal outcomes 1
• Obtain informed consent and conduct DNAR discussions prior to surgery 3

Anesthesia and Medications

• Administer either spinal or general anesthesia - both are appropriate with no superiority of one over the other 3
• Give prophylactic antibiotics within 1 hour of skin incision 1
• Implement active warming strategies to prevent hypothermia 1, 4
• Consider preoperative femoral nerve block for multimodal analgesia 3

Surgical Technique

Patient Positioning

• Position the patient supine on a fracture table 1
• Apply traction to the affected limb 1
• Ensure the hip is in neutral rotation or slight internal rotation - this is critical for proper screw placement 1
• Obtain fluoroscopic AP and lateral views to confirm adequate positioning and reduction 5

Guidewire Insertion

• Make small percutaneous incisions through the lateral femoral cortex 1
• Insert guidewires in a modified triangular transverse pattern with two screws positioned proximally and one screw distally - this configuration avoids creating a stress riser in the subtrochanteric region that can lead to iatrogenic fracture 2
• Use fluoroscopy in both AP and lateral planes to guide wire placement 5
• A cannulated screw can be used as a drill guide and sleeve to direct the guide pin insertion and prevent deflection - this technique accelerates the procedure and minimizes soft tissue dissection 5
• Ensure guidewires achieve parallel placement and adequate purchase in the femoral head 6

Screw Insertion

• Use fully-threaded 6.5mm or 7.0mm cannulated screws inserted over the guidewires 1
• Ensure the threads cross the fracture site - this is essential for compression and stability 1
• Verify screw position with fluoroscopy in both planes before final tightening 6
• Precise operative technique is mandatory - technical errors are the primary cause of mechanical failure including non-union and malunion 6

Critical Technical Points

• Achieve anatomical reduction before screw insertion - inadequate reduction negatively influences consolidation rates and increases reintervention rates 7
• Avoid placing two screws in the inferior part of the femoral neck, as this creates a stress riser leading to subtrochanteric fracture in 3.6% of cases 2
• The position of screws within the femoral head does not significantly influence consolidation rates, but parallel placement is preferred 7, 6

Post-Operative Management

Immediate Post-Operative Care

• Continue active warming to prevent hypothermia 1
• Administer tranexamic acid to reduce blood loss and transfusion requirements 1
• Provide regular paracetamol for pain management 1, 3
• Use opioids cautiously, especially in patients with renal dysfunction; avoid codeine due to constipation and association with postoperative cognitive dysfunction 3

Thromboprophylaxis

• Administer fondaparinux or low molecular weight heparin (LMWH) for DVT prophylaxis 1, 3, 4

Mobilization

• Implement early mobilization protocols on postoperative day one if medically stable 1, 3
• Allow immediate weight-bearing as tolerated - this reduces DVT risk and improves functional recovery 1, 3

Follow-Up and Monitoring

• Monitor for complications including non-union (occurs in unstable fractures with inadequate reduction), avascular necrosis, and mechanical failure 7, 6
• Arrange outpatient DEXA scan and referral to bone health clinic for osteoporosis evaluation 3
• Consolidation is accomplished in 95% of stable, anatomically reduced fractures within 1 year 7

Common Pitfalls to Avoid

• Do not use this technique for displaced fractures (Garden III-IV) - these require arthroplasty 1, 7
• Avoid placing two screws inferiorly - this creates a subtrochanteric stress riser and increases fracture risk 2
• Do not accept inadequate reduction - this is the primary determinant of poor outcomes and should prompt consideration of revision or arthroplasty 7, 6
• Ensure precise technique - mechanical failures are almost always due to technical errors or wrong indication 6